Valve with exploding diaphragm



May 18, 1965 E. E KILMER ETAL 3,184,07

VALVE WITH EXPLODING DIAPHRAGM Filed Jan. 19, 1962 PULSE FIQE.

SOURCE IO 18 l6 5 TRIGGER INVENTORS.

UMT EARL E. KILMER RAYNER A. MONTGOMERY United States Patent 3,184,097 VALVE WITH EXPLGDENG DIAPAGM R Earl E. Khmer, College Park, and Rayner A. Montgomery, Silver Spring, Md, assignors to the United States of America as represented by the Secretary of the Na F iied .lan. 19, 1962, Ser. No. 167,452 4 (Iiaims. (til. 226-47) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to a high speed valve and more particularly to an explodable diaphragm which will confine a pressurized gas until actuated to effect the high speed release of the pressurized gas.

The shock tunnel is a device developed to study the reaction of aerodynamic shapes in high speed air flows. The essential components of the shock tunnel consist of a smooth bore barrel which is closed at both ends to confine a column of air therein; the muzzle end of the barrel opens into a test chamber in which is mounted the aerodynamic shape to be tested. At the other end of the barrel is an explosive chamber having a mixture of ex losive gases therein. When the gases in the explosive ch amber are ignited, the resulting shock wave breaks through the closure at that end of the barrel, travels down the tube breaking the closure at the other end, and the column of air confined therein is forced out at high speed to impinge upon the aerodynamic shape. Cameras and transducers then record the actionof the aerodynamic shape to the resulting high speed air flow.

In the past, the closing of the ends of the barrel to confine the column of air therein was accomplished by clamping a metal diaphragm over each end of the barrel to prevent the escape of the air therein until the proper time. The shock wave produced in the explosive chamher would then shatter the two metal diaphragms thus opening both ends of the barrel. The metal diaphragm at the muzzle end of the barrel, however, had a tendency to shatter due to the force of the shock wave, spraying jagged particles of metal into the test chamber, often severely damaging the aerodynamic shape and test chamher and interfering with the high speed flow of air due to the non-uniform initial opening thereof. The expenses incurred by damage to the expensive aerodynamic shape and the test chamber, and failure of many test shots in the shock tunnel render the continued use of the metal diaphragm at the muzzle end of the barrel undesirable.

An object of this invention is to provide a high speed explodable diaphragm for use at the muzzle end of the shock tunnel, which will effectively confine the column of air within the barrel until being quickly opened at the proper time by detonation thereof leaving only the products of combustion to be expelled into the test chamber.

Another object of this invention is to provide a means for closing the muzzle end of the barrel of a shock tube tunnel which will not cause damage within the test chamber or interfere with the flow of air therein.

A further object of this invention is to provide an ex tremely high speed valve for confining and then releasing any pressurized fluid where such a valve might be desirable.

In the drawing:

FIG. 1 is a schematic illustration of the essential elements of a shock tunnel with the invention installed therein;

FIG. 2 is an exploded view of the separate elements which make up one embodiment of the explodable diaphragm of the present invention; and

FIG. 3 is a cross sectional view of the details of the explodable diaphragm as installed at the muzzle of the shock tube barrel.

In FIG. 1, a long smooth bore barrel 10 is shown connected at its back end to an explosive chamber 11 and at its muzzle end to a test chamber 12. The explosive chamber 11 is a thick walled enclosure into which an explosive mixture, such as hydrogen, oxygen and helium may be introduced. The explosive chamber also contains a sparking mechanism 13, such as an ordinary spark. plug or its equivalent, connected to a pulse source 14 to initiate the explosion of the mixture within the chamber. The test chamber 12 consists of an air tight enclosure attached to the muzzle end of the barrel 10. The test chamber 12 is also attached to a vacuum pump (not shown), which may be used to evacuate the chamber before each test. A mounting device 15 is located within the chamber to allow the aerodynamic shape 16 to be placed in position in front of the muzzle of the barrel 10. At the back end of the chamber, is a metal diaphragm 17 separating the explosive chamber 11 from the interior of the barrel 10; the separation produced by the diaphragm 17 is air tight so that the barrel may be filled with a pressurized gas, such as air, without having the air mix with the explosive gases in the chamber 11. At the muzzle end of the barrel 10, the explodable diaphragm 18, shown generally in FIG. 1, separates the muzzle end of the barrel and the pressurized air therein from the evacuated test chamber 12. The explodable diaphragm 18 is connected through a detonator 19 to a trigger unit 2!) connected to be triggered by the ionization probe 21 placed within the barrel of the tube.

In operation, the explosive chamber 11 is filled with an explosive gas mixture, the barrel 10 is filled with pres surized air, and the test chamber 12 is evacuated. A pulse received from the source 14 initiates a spark from the sparking device 13 Within the chamber 11 causing an explosion therein. The explosion within the chamber 11 breaks the metal diaphragm 17 sending a shock wave down the barrel 10 towards the muzzle. As the shock wave reaches the position of the ion probe 21, its arrival is sensed by the probe which sends an electrical signal to actuate the trigger unit 2% and send a pulse at the right time to the detonator 19, which will then initiate the explosion of the explosive diaphragm 18. The ionization probe 21 is placed at a sufficient distance from the explodable diaphragm 18 such that the shock wave will only be a short distance from the position of the diaphragm 18 at the time as it is completely exploded; this is done by taking into account the inherent time delay caused by the detonator and trigger circuit and the burning time of the explosive diaphragm. This time delay may also be controlled by a delay unit rather than by the position of the probe.

The components of an explodable diaphragm which has given particularly good results is illustrated in FIG. 2. A circular disc 22 of a high velocity flexible explosive of sufiicient size to cover the muzzle opening of the barrel is cut from a flexible sheet explosive. The flexible sheet explosive used in this case has a high explosive constituent, such as pentaerythritol tetranitrate (PETN), combined in a suitable flexible matrix, such as rubber, and supplied in 0.050 inch thickness. The velocity of detonation of the flexible sheet explosive should be approximately 5,000 meters per second or greater and have suitable safety characteristics. A suitable flexible sheet explosive is produced by E. I. du Pont de Nemours & (30., Inc. and identified as EL-506; EL506 has a density of approximately 1.50 grams per cubic centimeter, a velocity ens go's? of detonation of 6,500 to 7,500 meters per second plus good heat stability and impact stability characteristics. It is desirable that the flexible explosive or its equivalent be'air tight and remain so under moderate air pressures. An air ti ht plastic film 23, such as Mylar or its equivalent, also cut in a circular disc shape but of larger diameter than the explosive disc 22, is placed behind the explosive disc. A strong flexible cloth disc of the same configuration and size as the plastic film 23 is placed on the other side of the plastic film; the flexible cloth may be of woven type nylon, such as is used as parachute cloth, or its equivalent. The cloth disc 24 provides added support strength to the explosive disc 22 and the film 23 to prevent'their expansion under pressure to the point of rupture. The plastic film 23 is placed between the explosive disc 22 and the cloth 24 for the dual purpose of adding to the air tight shield and of preventing the extrusion of the rubbery explosive disc 22 through the porous cloth 24, which would produce small pin holes for the escape of pressurized air through the explosive disc 22. An annular sheet explosive 25 with an explosive lead 26 cut from the flexible sheet is placed opposite the cloth to initiate the explosion of the diaphragm. A detonator device attached to the end of the explosive lead 26 causes explosion of the ring 25 which cuts through the cloth 24 and plastic film 23 to the disc 22, which is ignited thereby and explodes. The explosion of the entire diaphragm across a 1.5 inch diameter opening is completed in from six to eight microseconds. The products of combustion, which are the only things remaining after the explosion, contain no damaging particles which might injure the aerodynamic shape under test. Also, the relatively small power of the diaphragm explosion has a negligible distorting effect on the advancing shock wave which is of much greater intensity.

In FIG.3, a holding device at the muzzle of the barrel holds the components in place for proper operation.

The holding device for clamping the explosive diaphragm in place consists of a hard metallic ring 27 within an inside diameter equal to the diameter .of the barrel 10 'to approximate an extension of the muzzle. A right angle groove, 28 is cut-into the clamping device 27 and a similar right angle groove 29 is cut into the face of the muzzle around the full inside diameter with the depths of both grooves closely approximating the thickness of the explosive sheet. A ring groove 31 with male and female portions. abutting on the face of the clamping device 27 and the face of the muzzle respectively are provided to' provide tight clamping of the plastic film 23 and cloth 24.

the. placement of the explosive sheet into the rectangular" grooves provides the necessary pressure thereon when the bolts 32 are fully tightened. The ring groove 31 on the outside of the rectangular groove allows the plastic film and the cloth to be tightly clamped toprovide the necessary support, strength and air tightness. The clamping device also contains a lead in passage 33 through which, the explosive lead 26 may be attached to the detonator or electric blasting cap 19. v V 1 7 V When the diaphragm is clamped in place, the pressure of the air in the barrel it) pushes on the explosive disc' of up to 1,000 lbs. per square inch. When Mylar film only was'used as a reinforcement, pressure differentials ot up to 575 lbs. per square inch could be maintained.

The sheet explosive alone Without reinforcing material 'Was ineitective at pressures less than 100 lbs. per square inch.

It will be observed that the explosive diaphragm provides a simple and extremely quick means of containing a pressurized fluid and suddenly releasing that fluid. Thus, the present invention may be easily adapted by anyone skilled in the art as a quick acting valve in any number of diiTerent situations. The valve in the present instance acts with such speed that in'the six to eight microseconds necessary for the valve to be completely opened, the shock wave will have traveled a bare four to five inches in the shock tunnel.

' It will be understood that various changes in the details,

" materials and arrangements of parts, which have been herein described and illustrated in this embodiment, in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention, as expressed in the appended claims. 7

What is claimed is:

1. An explodable diaphragm arrangement to provide a high speed valve for suddenly releasing pressurized gas from an opening'comprising a continuous sheet of'high velocity flexible explosive for covering said opening, an air tight plastic film, a sheet of flexible woven plastic material, said film and said ,woven material being flammable, a second sheet of high velocity flexible explosive having an'aperture therein at the center thereof the size of said-opening, holding means for securely holding said continuous sheet across said opening with one side thereof in contact with said pressurized gas, for tightly clamping said film and said sheet of Woven material against said continuous film 'on the opposite side of said film to provide reinforcement therefor, and for holding said second sheet against said film and said woven material, and detonating means connected to said second sheet, whereby actuation of said detonating means opens said diaphragm.

2. The improvement of claim 1 wherein said sheet consists of PETN. suspended in a flexible matrix; 3. The improvement of claim 1 wherein said film is fonned of Mylar. V

4. The improvement of claim 1 wherein said plastic material is woven of nylon.

References Cited by the Examiner .UNITED STATES PATENTS THERON E. CONDON, Primary Examiner. DAVID SCHONBEVRG, Examiner. 

1. AN EXPLODABLE DIAPHRAGM ARRANGEMENT TO PROVIDE A HIGH SPEED VALVE FOR SUDDENLY RELEASING PRESSURIZED GAS FROM AN OPENING COMPRISING A CONTINUOUS SHEET OF HIGH VELOCITY FLEXIBLE EXPLOSIVE FOR COVERING SAID OPENING, AN AIR TIGHT PLASTIC FILM, A SHEET OF FLEXIBLE WOVEN PLASTIC MATERIAL, SAID FILM AND SAID WOVEN MATERIAL BEING FLAMMABLE, A SECOND SHEET OF HIGH VELOCITY FLEXIBLE EXPLOSIVE HAVING AN APERTURE THEREIN AT THE CENTER THEREOF THE SIZE OF SAID OPENING, HOLDING MEANS FOR SECURELY HOLDING SAID CONTINUOUS SHEET ACROSS SAID OPENING WITH ONE SIDE THEREOF IN CONTACT WITH SAID PRESSURIZED GAS, FOR TIGHTLY CLAMPING SAID FILM AND SAID SHEET OF WOVEN MATERIAL AGAINST SAID CONTINUOUS FILM ON THE OPPOSITE SIDE OF SAID FILM TO PROVIDE REINFORCEMENT THEREFOR, AND FOR HOLDING SAID SECOND SHEET AGAINST SAID FILM AND SAID WOVEN MATERIAL, AND DETONATING MEANS CONNECTED TO SAID SECOND SHEET, WHEREBY ACTUATION OF SAID DETONATING MEANS OPENS SAID DIAPHRAGM. 